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Biodiversity and Evolution
Chapter 4
25
Biology
Undergraduate 1
09/25/2011

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Term
adaptation, or adaptive trait
Definition
any heritable trait that enables an individual organism to survive through natural selection and to reproduce more than other individuals under prevailing environmental conditions.
Term
background extinction
Definition
Throughout most of history, species have disappeared at a low rate, called background extinction.
Term
biological diversity, or biodiversity
Definition
the variety of the earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life.
Term
biological evolution
Definition
the process whereby earth’s life changes over time through changes in the genes of populations.
Term
differential reproduction
Definition
For natural selection to occur, a trait must be heritable, meaning that it can be passed from one generation to another. The trait must also lead to differential reproduction, which enables individuals with the trait to leave more offspring than other members of the population leave.
Term
ecological niche
Definition
Scientists describe the role that a species plays in its ecosystem as its ecological niche, or simply niche (pronounced “nitch”). It is a species’ way of life in a community and includes everything that affects its survival and reproduction, such as how much water and sunlight it needs, how much space it requires, and the temperatures it can tolerate.
Term
endemic species
Definition
Species that are found in only one area are called endemic species and are especially vulnerable to extinction.
Term
extinction
Definition
Another process affecting the number and types of species on the earth is extinction, in which an entire species ceases to exist.
Term
fossils
Definition
Most of what we know of the earth’s life history comes from fossils: mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items found in rocks.
Term
foundation species
Definition
Another important type of species in some ecosystems is a foundation species, which plays a major role in shaping communities by creating and enhancing their habitats in ways that benefit other species.
Term
generalist species
Definition
Generalist species have broad niches. They can live in many different places, eat a variety of foods, and often tolerate a wide range of environmental conditions.
Term
geographic isolation
Definition
occurs when different groups of the same population of a species become physically isolated from one another for long periods.
Term
indicator species
Definition
Species that provide early warnings of damage to a community or an ecosystem are called indicator species.
Term
keystone species
Definition
A keystone is the wedge-shaped stone placed at the top of a stone archway. Remove this stone and the arch collapses. In some communities and ecosystems, ecologists hypothesize that certain species play a similar role. Keystone species have a large effect on the types and abundances of other species in an ecosystem.
Term
mass extinction
Definition
is a significant rise in extinction rates above the background level.
Term
mutations
Definition
The first step in this process is the development of genetic variability in a population.This genetic variety occurs through mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.
Term
native species
Definition
are those species that normally live and thrive in a particular ecosystem.
Term
natural selection
Definition
Darwin and Wallace concluded that these survival traits would become more prevalent in future populations of the species through a process called natural selection, which occurs when some individuals of a population have genetically based traits that enhance their ability to survive and produce offspring with the same traits.
Term
nonnative species
Definition
Other species that migrate into or are deliberately or accidentally introduced into an ecosystem are called nonnative species, also referred to as invasive, alien, or exotic species.
Term
reproductive isolation
Definition
mutation and change by natural selection operate independently in the gene pools of geographically isolated populations.
Term
specialist species
Definition
In contrast, specialist species occupy narrow niches. They may be able to live in only one type of habitat, use one or a few types of food, or tolerate a narrow range of climatic and other environmental conditions.
Term
speciation
Definition
Under certain circumstances, natural selection can lead to an entirely new species. In this process, called speciation, two species arise from one.
Term
species diversity
Definition
An important characteristic of a community and the ecosystem to which it belongs is its species diversity the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species (species evenness).
Term
species evenness
Definition
An important characteristic of a community and the ecosystem to which it belongs is its species diversity: the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species (species evenness).
Term
species richness
Definition
An important characteristic of a community and the ecosystem to which it belongs is its species diversity: the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species (species evenness).
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